From long before the dawn of civilization to the present day, hominids have faced a choice of how much of their food to eat and how much to save for future uses, particularly planting, future consumption and animal feed. It is important that certain and perhaps different qualities be preserved over the storage periods for both food and seed. More recently hominids have introduced commerce, and into commerce various other commodities, many of which require special storage conditions. Maintaining optimal storage conditions usually implies sealing to prevent exchange with the environment. Throughout history and prehistory hominids have stored commodities, including agricultural products, in a variety of containers. Perhaps the best success with storage has been realized in glass, ceramic and metal containers. It long has been observed that many commodities are better preserved in the absence of oxygen, moisture or both. This would be the case if only because insects and rodents are unable to eat in the absence of air or oxygen, but also because preventing or minimizing exposure to oxygen and moisture retards spoilage by oxidation, microbes and hydrolysis.
Below a certain water activity level, bacteria and molds are incapable of activity. Many bacteria and fungi also are unable to function in the absence of oxygen. Thus, it would be beneficial if closing devices for containers could be manufactured to seal in ways that provide strong barriers to ingress of oxygen, moisture and other environmental substances. In some cases, stored commodities are susceptible to losses by evaporation, including loss of volatiles, where strong barriers can provide additional protection of product quality. For example, by preventing loss of flavors or essential oils. By strong is meant low permeability.
In recent centuries, Herculean efforts have been expended to achieve better sealing of containers in science, engineering, art and commerce. Many of these efforts are represented in the patent, technical and scientific literature. The best prior art approaches to achieve high quality sealing include metal-to-metal contact with pressure or fusion and metal-to-glass contact with pressure, chemical bonding, fusion or some combination thereof. Continuous contact and considerable pressure generally are required to seal metal to glass and metal to metal, necessitating precision machined hardware, high torque values, multiple fasteners or other relatively expensive measures. These approaches generally have not been feasible for containers employed in routine commerce of commodities, both because of the expense of precision high-strength hardware and close-tolerance manufacture, and the fact that these approaches are not suited to high-speed processing.
Thus, the standard practice in commerce has been to manufacture glass jars with metal or plastic closures, where the seal is made with a thin gasket of inexpensive and often toxic polymer. In many cases, the plasticized polymer is permanently bonded to a metal closure using a plastisol process. Many plastisol seals utilize endocrine disruptors or other toxic compounds as plasticizers, which, all other things being equal, are undesirable for use in food containers, except in cases where profits are preferred over customer safety. In the case of metal cans, the seams often are sealed with plastisol during rolling and crimping, which provides an effective barrier against microbial contamination and dust, but not against ingress of oxygen and moisture, nor egress of volatiles. Clay containers are quite rare in modern commerce, but were important in ancient times. Were it possible to seal them well, they might play a more important role in future commerce.
Unfortunately, the polymers used to seal almost all containers of commerce are invariably permeable to gases and vapors, the inexpensive polymers moreso than others. The plasticizers in plastisols, particularly phthalates and oxygenated oils, are susceptible to migration into products held in the containers. In fact, there are very few, if any, polymers that are able to effectively block migration of gases and vapors. There is a wide range of barrier effectiveness across the many families of polymers.
In light of the discussion above, there is required a closure and an assembly of the closure with a container, that does not suffer from above mentioned deficiencies.
Throughout this specification, unless the context requires otherwise, the words “comprise”, “comprises” and “comprising” will be understood to imply the inclusion of a stated step or element or group of steps or elements but not the exclusion of any other step or element or group of steps or elements.
Any one of the terms: “including” or “which includes” or “that includes” as used herein is also an open term that also means including at least the elements/features that follow the term, but not excluding others.
Any discussion of the background art throughout the specification should in no way be considered as an admission that such background art is prior art nor that such background art is widely known or forms part of the common general knowledge in the field in the U.S. or anywhere else.